Apoptosis is a type of programmed death of a cell, in which phenomena such as lack of contact with the surrounding cells, inspissation of cytoplasm, aggregation of chromatin and karyopyknosis related to the activity of endonuclease, fragmentation of nucleus, the cell being changed into membrane-wrapped bulboid corpuscles, englobement of the bulboid corpuscles by the adjacent macrophage or epithelial cells, or fragmentation of the nucleosome unit of DNA into DNA fragments of 180–200 base length by the activity of endonuclease are observed. Apoptosis has been discussed as a mechanism in which the final fragments of apoptic somatic cells exhibiting the aforementioned phenomena are englobed by the adjacent cells (e.g., “Immunology Today”, 7:115–119. 1986: Science 245:301–305. 1989).
As the gene that controls the apoptosis described above, the bcl-2 gene, which is one of oncogene discovered from B cell lymphoma in 1985, is known. This bcl-2 gene appears quite frequently in cells of the immune system or neuronal cells. It is assumed that the substance produced as a result of expression of the gene suppresses the apoptosis of such cells, whereby the function of the human immune and neuronal systems are constantly maintained the homeostasis thereof. In addition, as the bcl-2 gene appears in a fetus in an especially wide range, it is assumed that the gene plays an important role in morphogeny during the ontogenic process.
On the other hand, the inventors of the present application have isolated Neuronal Apoptosis Inhibitory Protein (NAIP) gene, as the gene causing Spinal Muscular Atrophy (SMA) which is a familial genetic disease, from the human chromosome 5q13.1 domain (Roy et al., Cell 80: 167–178, 1995), and they have filed a patent application for the gene (PCT/CA95/00581). Specifically, it is considered that the mutation of the NAIP gene or the decrease in the number of copies therefrom causes apoptosis of spinal neurons, resulting in the development of SMA. Further, in a case in which the NAIP gene is introduced into various cultured cells and stimulation is provided to the cells to induce apoptosis, it has been found out that the death of the cells is significantly prevented (Liston et al., “Nature” 379: 349–353, 1996). In this case, it has also been found out that NAIP functions as the apoptosis inhibitory factor not only to the neuronal cells but also to the somatic cells as a whole.
The inventors of the present application have isolated the full amino acid sequence of NAIP and cDNA encoding the NAIP, and filed a patent application thereof (Japanese Patent Application No. 9-280831).
As described above, NAIP is a protein which is concerned with various apoptosis-related diseases including SMA. In order to understand the mechanism of a patient's developing such diseases, diagnose the risk for developing the diseases, prevent the development of the diseases or reduce the severity of the diseases, and develop the medical technique and medicines for treatment, it is essential to accurately assay the amount of expressed NAIP.
The inventions of the present application has been contrived in consideration of the aforementioned task, and objects of the present invention is to provide anti-NAIP monoclonal antibodies, which are essential for assaying NAIP and a NAIP assaying method using the monoclonal antibodies.